Can i run my truck with headers and no cats before tune? the tune is on the way and i can wait, but want to install headers tomorrow and hear it run! The reason I'm asking is i read in another thread that it would run and rich and turn the engine light on. So this is my question: the tune form asks if there are any trouble codes present and as of right now there isn't(still stock) so will this mess anything up if run it? i wouldn't think it would or at least it will be corrected as soon as pcm is changed out. kind of sounds like a dumb question but figured id ask anyway